Check valve



FIG. 1 is a top, front perspective view of a check valve;

FIG. 2 is a top, rear perspective view thereof;

FIG. 3 is a side view thereof;

FIG. 4 is a front view thereof;

FIG. 5 is a rear view thereof; and,

FIG. 6 is a top view thereof.

The broken lines showing for unclaimed portions of the check valve in FIGS. 1–2 and 4–6 form no part of the claimed design. 

The ornamental design for a check valve, as shown and described. 